.\"
.\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for
.\" permission to reproduce portions of its copyrighted documentation.
.\" Original documentation from The Open Group can be obtained online at
.\" http://www.opengroup.org/bookstore/.
.\"
.\" The Institute of Electrical and Electronics Engineers and The Open
.\" Group, have given us permission to reprint portions of their
.\" documentation.
.\"
.\" In the following statement, the phrase ``this text'' refers to portions
.\" of the system documentation.
.\"
.\" Portions of this text are reprinted and reproduced in electronic form
.\" in the SunOS Reference Manual, from IEEE Std 1003.1, 2004 Edition,
.\" Standard for Information Technology -- Portable Operating System
.\" Interface (POSIX), The Open Group Base Specifications Issue 6,
.\" Copyright (C) 2001-2004 by the Institute of Electrical and Electronics
.\" Engineers, Inc and The Open Group.  In the event of any discrepancy
.\" between these versions and the original IEEE and The Open Group
.\" Standard, the original IEEE and The Open Group Standard is the referee
.\" document.  The original Standard can be obtained online at
.\" http://www.opengroup.org/unix/online.html.
.\"
.\" This notice shall appear on any product containing this material.
.\"
.\" The contents of this file are subject to the terms of the
.\" Common Development and Distribution License (the "License").
.\" You may not use this file except in compliance with the License.
.\"
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
.\" or http://www.opensolaris.org/os/licensing.
.\" See the License for the specific language governing permissions
.\" and limitations under the License.
.\"
.\" When distributing Covered Code, include this CDDL HEADER in each
.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
.\" If applicable, add the following below this CDDL HEADER, with the
.\" fields enclosed by brackets "[]" replaced with your own identifying
.\" information: Portions Copyright [yyyy] [name of copyright owner]
.\"
.\"
.\" Copyright 1989 AT&T
.\" Copyright (c) 1997, The Open Group. All Rights Reserved.
.\" Portions Copyright (c) 2001, Sun Microsystems, Inc.  All Rights Reserved
.\"
.TH ATEXIT 3C "May 25, 2001"
.SH NAME
atexit \- register a function to run at process termination or object unloading
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBatexit\fR(\fBvoid (*\fR\fIfunc\fR)(void));
.fi

.SH DESCRIPTION
.sp
.LP
The \fBatexit()\fR function registers the function pointed to by \fIfunc\fR to
be called without arguments on normal termination of the program or when the
object defining the function is unloaded.
.sp
.LP
Normal termination occurs by either a call to the \fBexit\fR(3C) function or a
return from \fBmain()\fR. Object unloading occurs when a call to
\fBdlclose\fR(3C) results in the object becoming unreferenced.
.sp
.LP
The number of functions that may be registered with \fBatexit()\fR is limited
only by available memory (refer to the \fB_SC_ATEXIT_MAX\fR argument of
\fBsysconf\fR(3C)).
.sp
.LP
After a successful call to any of the \fBexec\fR(2) functions, any functions
previously registered by \fBatexit()\fR are no longer registered.
.sp
.LP
On process exit, functions are called in the reverse order of their
registration. On object unloading, any functions belonging to an unloadable
object are called in the reverse order of their registration.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, the \fBatexit()\fR function returns 0. Otherwise,
it returns a non-zero value.
.SH ERRORS
.sp
.LP
The \fBatexit()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Insufficient storage space is available.
.RE

.SH USAGE
.sp
.LP
The functions registered by a call to \fBatexit()\fR must return to ensure that
all registered functions are called.
.sp
.LP
There is no way for an application to tell how many functions have already been
registered with \fBatexit()\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR exec (2),
.BR dlclose (3C),
.BR exit (3C),
.BR sysconf (3C),
.BR attributes (7)
